Since the fluorescence of anthracene was reported in 1960s, research and development as to various substances emitting fluorescence have been actively done. In particular, there have been ongoing studies on different fluorescent substances usable for luminous substances in an organic light emitting diode, an organic solar cell, or the like, and vigorous researches have been conducted particularly on the polymeric fluorescent substance.
For example, since a conjugated polymer with π-conjugations (i.e., the portion where a saturated bonding and an unsaturated bonding exist in an alternating manner) was found to emit fluorescence due to its molecular rotation or vibration, many efforts have been exerted on using it as a polymeric fluorescent substance.
Furthermore, an isotactic polystyrene polymer having a stacked structure made of a plurality of phenyl groups in the repeating units has been reported almost uniquely to show fluorescence thanks to the presence of the stacked structure of the phenyl groups, despite the fact that it is an unconjugated polymer.
While the fluorescent conjugated polymers hitherto known in the art have some degree of fluorescence efficiency in their liquid state as being dissolved in a solvent with a high solubility, most of them show a low level of fluorescence efficiency when being in a solid state or being added to a solvent with a very low solubility. For this reason, the fluorescent conjugated polymers have found difficulties in being prepared as a thin film and thus their application for the luminous substance in the organic light emitting diode or the organic solar cells or for other various uses has been virtually limited, as well.
Moreover, the unconjugated isotactic polystyrene polymer has also had limits on its uses as a luminous substance in various fields because it shows merely an insufficient level of fluorescence and its production that entails using a special catalyst has been of great difficulty.
In addition, previously known fluorescent substances are predominantly typified in selectively emitting light of a certain wavelength only, and thus, emitting white or pale blue light close to white often requires using a plurality of fluorescent substances, and this has become one reason for making components for devices such as an organic light emitting diode or their production process more complicated.
In respect of the aforementioned problems, there remains a need to develop a novel polymeric fluorescent material capable of exhibiting fluorescence very efficiently even in a solid state and available for a white or blue light emitting substance.